WASHINGTON,, United States (AFP) — US online giant Amazon on Thursday unveiled plans to launch grocery delivery to a number of US cities for its Prime subscriber using its recently acquired Whole Foods supermarket chain.

While Amazon has previously offered limited grocery delivery, the new Prime Now service offers a wider selection of fresh items with service in one or two hours, stepping up competition against rivals such as Instacart and Peapod.

It is the first major effort to integrate Whole Foods -- a chain of 460 stores -- into Amazon's e-commerce effort.

The service was available as of Thursday in Austin and Dallas, Texas; Cincinnati, Ohio; and Virginia Beach, Virginia. But Amazon said it has plans to expand the service to other cities soon.

Customers can order "fresh produce, high quality meat and seafood, everyday staples and other locally sourced items from Whole Foods Market" using a mobile Prime Now application from Amazon.

Prime Now will also deliver from other grocery stores and restaurants in the markets where it operates.

"We're happy to bring our customers the convenience of free two-hour delivery through Prime Now and access to thousands of natural and organic groceries and locally sourced favorites," said John Mackey, Whole Foods Market co-founder and chief executive.

Amazon Prime members receive two-hour delivery for free and delivery within one hour for US$7.99 on orders of US$35 or more, according to a statement.

Amazon, which has grown from its origins as an online bookseller to a global behemoth in retail, cloud computing, online video and other services, has made founder Jeff Bezos the world's richest individual.